The country star (who shared her own wedding photo with PEOPLE!) will team up with Train lead singer Pat Monahan for a duet of “Marry Me” in honor of Christina Davidson and Frank Tucci. The couple met under unusual and heartbreaking circumstances – at a grief support group where both were mourning the loss of their spouses.

“I’m looking forward to just sharing in their moment,” McBride, 45, tells PEOPLE. “When I read their story, I felt an emotional connection. They have been through so much and I just thought about what an honor it would be to share this moment with them.”

Of the song selection for the big day, she adds: “Every line is so heartfelt. I hadn’t heard anything like it before.”

In the spirit of all the nuptial talk surrounding this year’s ACM awards, McBride – who will celebrate her 24th wedding anniversary with husband John McBride on May 15 – shared some of her favorite memories from her own wedding day.

“There are so many,” she says. “Going to breakfast with my mom and sister. Walking down the aisle with my dad. The kiss. Walking back down the aisle as the new Mrs. McBride! It was magical day.”

The ACM Awards, hosted by Reba McEntire and Blake Shelton, air at 8 p.m. ET on CBS. People.com will be live blogging all the action!